The problem is clear: MMA is copying the artist tag to album artist, for example:
I have in MMW a file that has this properties:

Artist: Jarrett - Peacock - DeJohnette
Album Artist: Keith Jarrett

In the Media Tree in MMW i see this files under Album Artist > Keith Jarrett. So that´s ok.

but after syncing, in MMA i see them under Album Artist > Jarrett - Peacock - DeJohnette, and if i go to properties for those files, "Album Artist" has been changed to Jarrett - Peacock - DeJohnette, copying the Arist Tag, and the same with other files, so I get this in my Album Artist view: (where i should have one entry only)

Ok, I factory reset the phone (Sony Z3c) and it solved that problem, but now all the album art is missing and... songs won't even play. Nothing happens. No problem in other apps. Thanks for the help rusty, but I quit.

I'm having this same problem with an Xperia z5c. I'm syncing with MMW (both USB and wifi). MMA is calling the Album artist what is actually the artist for either the first or last track of an album. But the albums are also correctly listing under the album artist (e.g. Various Artists) as far as I can see.

e.g. William Elliott Whitmore is just an artist on the VA comp Germs of Perfection:
but I realised, looking at the details of the tracks in this case that the wrong ones point to files that don't exist. I'm not sure if the file has previously existed or why it says a different duration.